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Zijun Hu 72cd71ec60 char: misc: Make misc_register() reentry for miscdevice who wants dynamic minor 
[ Upstream commit 52e2bb5ff0 ]

For miscdevice who wants dynamic minor, it may fail to be registered again
without reinitialization after being de-registered, which is illustrated
by kunit test case miscdev_test_dynamic_reentry() newly added.

There is a real case found by cascardo when a part of minor range were
contained by range [0, 255):

1) wmi/dell-smbios registered minor 122, and acpi_thermal_rel registered
   minor 123
2) unbind "int3400 thermal" driver from its device, this will de-register
   acpi_thermal_rel
3) rmmod then insmod dell_smbios again, now wmi/dell-smbios is using minor
   123
4) bind the device to "int3400 thermal" driver again, acpi_thermal_rel
   fails to register.

Some drivers may reuse the miscdevice structure after they are deregistered
If the intention is to allocate a dynamic minor, if the minor number is not
reset to MISC_DYNAMIC_MINOR before calling misc_register(), it will try to
register a previously dynamically allocated minor number, which may have
been registered by a different driver.

One such case is the acpi_thermal_rel misc device, registered by the
int3400 thermal driver. If the device is unbound from the driver and later
bound, if there was another dynamic misc device registered in between, it
would fail to register the acpi_thermal_rel misc device. Other drivers
behave similarly.

Actually, this kind of issue is prone to happen if APIs
misc_register()/misc_deregister() are invoked by driver's
probe()/remove() separately.

Instead of fixing all the drivers, just reset the minor member to
MISC_DYNAMIC_MINOR in misc_deregister() in case it was a dynamically
allocated minor number, as error handling of misc_register() does.

Cc: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Signed-off-by: Zijun Hu <zijun.hu@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250714-rfc_miscdev-v6-5-2ed949665bde@oss.qualcomm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-11-13 15:34:14 -05:00
arch s390/pci: Use pci_uevent_ers() in PCI recovery 2025-11-13 15:34:12 -05:00
block blk-cgroup: fix possible deadlock while configuring policy 2025-11-13 15:34:07 -05:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: essiv - Check ssize for decryption and in-place encryption 2025-10-19 16:33:42 +02:00
Documentation dpll: spec: add missing module-name and clock-id to pin-get reply 2025-11-13 15:33:59 -05:00
drivers char: misc: Make misc_register() reentry for miscdevice who wants dynamic minor 2025-11-13 15:34:14 -05:00
fs smb: client: fix potential cfid UAF in smb2_query_info_compound 2025-11-13 15:33:56 -05:00
include s390/pci: Use pci_uevent_ers() in PCI recovery 2025-11-13 15:34:12 -05:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:33:50 +02:00
io_uring io_uring/zctx: check chained notif contexts 2025-11-13 15:34:03 -05:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel uprobe: Do not emulate/sstep original instruction when ip is changed 2025-11-13 15:34:07 -05:00
lib kunit: test_dev_action: Correctly cast 'priv' pointer to long* 2025-11-13 15:33:57 -05:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm: prevent poison consumption when splitting THP 2025-10-29 14:08:57 +01:00
net net: ipv6: fix field-spanning memcpy warning in AH output 2025-11-13 15:34:12 -05:00
rust mm/ksm: fix flag-dropping behavior in ksm_madvise 2025-10-23 16:20:47 +02:00
samples ftrace/samples: Fix function size computation 2025-09-19 16:35:44 +02:00
scripts gcc-plugins: Remove TODO_verify_il for GCC >= 16 2025-10-06 11:17:52 +02:00
security KEYS: trusted_tpm1: Compare HMAC values in constant time 2025-10-19 16:33:51 +02:00
sound ASoC: mediatek: Use SND_JACK_AVOUT for HDMI/DP jacks 2025-11-13 15:34:10 -05:00
tools selftests/net: Ensure assert() triggers in psock_tpacket.c 2025-11-13 15:34:10 -05:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-07-17 18:37:08 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-08-01 09:48:44 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: Update Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Linux 6.12.57 2025-11-02 22:15:23 +09:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.